1. Field of the Invention
The present invention generally relates to lightwave communications systems and, more particularly, to a method and apparatus for controlling power transients in an optical communication system.
2. Description of the Related Art
In the field of fiber optic communications, it has been known for some time to increase the capacity of an optical communications link by propagating wavelength-division multiplexed (WDM) optical signals along optical fibers. Specifically, a WDM signal is composed of a plurality of distinct wavelengths of light, each such wavelength carrying a respective optical information signal, also known as an information channel. The number of wavelengths (i.e., information channels) in a WDM signal is a system parameter and usually ranges from 2 to 128 (in the case of xe2x80x9cdensexe2x80x9d WDM, or DWDM).
As the WDM signal travels through an optical network, it gradually fades and must be amplified at various points along its route. Optical amplifiers are typically provided throughout the optical network to maintain optical signal levels at their correct power settings. Transients caused by the instantaneous addition or removal of one or more individual optical information channels by an add/drop multiplexer or other device will affect the power of the WDM signal. Such transients can cause some channels to have power levels that are too high or low with respect to other channels. These transients can cause substantial degradation in the system""s bit error rate and may affect service of the optical network.
The disadvantages associated with the prior art are overcome by a method and apparatus for controlling transients in an optical signal propagating along an optical fiber path interconnecting a plurality of network elements. The present invention detects a change in power of an optical signal in a first network element that exceeds a threshold. When the power of the optical signal exceeds the threshold, the first network element adjusts the power of the optical signal and transmits a transient notification to at least one additional network element. In one embodiment, the first network element adjusts the power of the optical signal by controlling at least one gain element disposed therein, to achieve a desired power per channel of the optical signal. In another embodiment, the present invention establishes a series of thresholds, and the response of the network elements disposed along an optical transmission line is dictated by which particular threshold has been exceeded.